Faraday Cages and Radar Assaults - Wikipedia (article link)

Faraday cages cannot block static and slowly varying magnetic fields, such as Earth's magnetic field (a compass will still work inside). To a large degree though, they also shield the interior from external electromagnetic radiation (radar for example) if the conductor is thick enough and any holes are significantly smaller than the radiation's wavelength.

For example, certain computer forensic test procedures of electronic components or systems that require an environment devoid of electromagnetic interference may be conducted within a screen room. These screen rooms are essentially work areas that are completely enclosed by one or more layers of fine metal mesh or perforated sheet metal.

The metal layers are grounded to dissipate any electric currents generated from the external electromagnetic fields and thus block a large amount of the electromagnetic interference. See also electromagnetic shielding.

The reception of external radio signals, a form of electromagnetic radiation, through an antenna within a cage can be greatly attenuated or even completely blocked by the cage itself.

2. The metal layers are grounded to dissipate any electric currents generated from the external electromagnetic radiation (ex: radio waves, radar).

3. The reception of external radio signals, a form of electromagnetic radiation (radar for example), through an antenna within a cage can be greatly attenuated or even completely blocked by the cage itself.